Light and Sound 3D Imaging That Fits on a Needle Could Revolutionize Endoscopy

Led by King's College London researchers, a recent study demonstrates a photoacoustic imaging endoscope probe that fits inside a medical needle, with a diameter of only 0.6 millimeters.

Smallest Photoacoustic Endoscopy Probe

(Photo: MART PRODUCTION / Pexels)

Combining light and sound imaging to render 3D images can only be achieved with photoacoustic imaging. Despite providing valuable clinical information, the instrument is often too slow for practical use or too bulky.

Wenfeng Xia, the lead researcher, says that traditional light-based endoscopes provide tissue anatomical information on the surface and tend to have large footprints. On the other hand, the team's recently developed thin endoscope that can fit on a medical needle can resolve subcellular-scale tissue structural and molecular information in real-time. The device, which is small enough to be integrated with other medical devices, would allow clinicians to characterize tissue during various procedures, reports EurekAlert.

The ultra-thin endoscope developed by researchers from King's College London and the University College of London described the probe in the journal Biomedical Optics Express, titled "Ultrathin, high-speed, all-optical photoacoustic endomicroscopy probe for guiding minimally invasive surgery," consists of two optical fibers with the diameter of human hair.

Xia explains that the speed of photoacoustic endomicroscopy imaging using the new probe is two orders of magnitude higher than conventionally used. Eventually, the device would allow 3D tissue characterization during different minimally invasive procedures, like tumor biopsies. This could also help clinicians pinpoint the right area to sample, increasing the diagnosis's accuracy.

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Understanding Photoacoustic Imaging

The procedure works by shining light pulses onto light-absorbing structures in the body, like red blood cells and DNA. Structures then generate acoustic waves detected by ultrasound sensors and use the data to form images that resolve molecular, structural, and functional information from below the surface of the tissue.

Although experts have already developed fiber-based photoacoustic endoscopy probes, they require bulky ultrasound detectors with low imaging speeds. In the recent study, researchers overcame the many challenges of the procedure by combining wavefront-based beams with light-based ultrasound detection and a high-speed algorithm for device manipulation.

The unique combination allowed experts to create a small probe without sacrificing its imaging speed.

The newly created probe uses two thin optical fibers - one for delivering light pulses to generate acoustic waves and the other for ultrasound detection. For the excitation light, high-speed digital micromirror devices are used to scan a tightly focused light spot. The device has nearly a million tiny mirrors independently flipped at tens of thousands of frames per second to change the wavefronts of the light so it can be focused and scan the tissue.

For ultrasound detection, researchers developed an optical microresonator - a small structure made for confining light - that can be fabricated on the tips of optical fibers; when sound waves hit the optical microresonator, its thickness changes which modify the amount of light reflected into the fiber, allowing optical detection of the acoustic waves.

The team is hopeful that it will revolutionize clinical imaging.